a statistics problem, please help?

Question

there is evidence to suggest that certain herbs can have an effect on human memory. A researcher plans to use a standardized memory test to evaluate the effect of the herbs. Scores on the standardized test form a normal shaped distribution of, standard deviation 15 and a mean of 70. The researcher obtains a sample on N=25 people and has each person take an herbal supplement every day for 30 days. At the end of the 30 day period, each person takes the standardized memory test and the mean score for the sample is calculated to be M=78


b)identify the critical region for the test assuming that the researcher is using alpha level =.05

Answer 1

If the test is

H0: mean = 70
Ha: mean > 70

Critical region: M > 70 + (15/sqrt(25))z_0.95 = 70 + 3*1.645 = 74.935